Unsolicited Bulk Email (UBE) is a widespread problem. UBE may include unsolicited commercial email, spam, phishing email and other unsolicited bulk emails. Originators of UBE (spammers) harness the processing power of numerous mail server machines to send UBE. Large-scale Email Service Provid, ers (ESPs) are disadvantaged in processing UBE by the sheer magnitude of their mailing infrastructure and inbound email accepting capacity.
UBE messages can have a number of characteristics which identify them as UBE to ESPs. ESPs generally use a number of mechanisms to reduce the amount of UBE that users of the system receive. Consequently, spammers use a variety of techniques to circumvent the efforts of ESPs to stop their messages. Spammers constantly change routes, domain names, origination IPs, and message content to fool UBE detection systems.